What are the elements that form interference in electronic systems

Electromagnetic interference and the hazards when unwanted voltages and currents affect the performance of the equipment, known as the existence of electromagnetic interference, these voltages and currents can be conducted or electromagnetic field radiation on the victim equipment to produce undesired effects. The formation of electromagnetic interference must be accompanied by three factors: (1) the source of electromagnetic interference, or "transmitter"; (2) the "receiver" sensitive to this type of interference energy; (3) the energy from the source of the interference coupled to the receiver, and make the system performance significantly worse. medium, or coupling channel, that deteriorates system performance. The "emitter" refers to the source of electromagnetic energy, and the "receiver" (susceptor) refers to the electromagnetic energy response equipment. From the source of interference, electromagnetic interference can be divided into natural and man-made sources of interference. Natural sources of interference include the earth's thunderstorms, lightning generated by the sky electric noise, sunspot explosions and activities generated by the noise and the Milky Way cosmic noise. Man-made sources of interference are electromagnetic interference generated by electromechanical or other artificial devices, which include: various radio transmitters; industrial, scientific and medical radio-frequency equipment; overhead power lines, high-voltage equipment and electric traction systems; electromechanical vehicles and internal combustion engines; electric motors, household appliances, lighting appliances and similar equipment; information technology equipment; and electrostatic discharge and electromagnetic pulse. With the development of science and technology and productivity and the improvement of people's living standards, the types of man-made interference sources continue to increase, the electromagnetic interference generated by the increasingly serious pollution of the environment. At present, man-made interference has become the main source of electromagnetic environment level. From the propagation path of interference to points, electromagnetic interference can be divided into: conduction interference and radiation interference. Along the wire transmission of electromagnetic interference is called conduction interference. Electronic system between the equipment or electronic equipment between the unit circuit there are a variety of wires, so it is possible to make a device (or unit circuit) of electromagnetic energy along such wires to other equipment and unit circuit, thus causing interference. Radiated interference is electromagnetic interference that propagates through space. Interference source of the circuit, input and output signal circuits and control circuits and other wires under certain conditions can constitute a radiating antenna or receiving antenna. If the shell of the source of interference flows through the high frequency current, this shell itself also becomes a radiation antenna or receiving antenna. From the effect of electromagnetic interference to the division, electromagnetic interference including system interference and system interference between two aspects. Electromagnetic interference is very harmful to human beings, mainly manifested as follows: (1) Harm to electronic systems and equipment Strong electromagnetic interference may cause sensitive electronic equipment due to overload and damage. General silicon transistor emitter and base of the reverse breakdown voltage between 2 ~ 5V, it is easy to damage, and its reverse breakdown voltage with the temperature increases and decreases. Electromagnetic interference caused by the spike voltage can make the emitter junction and collector junction in a point of impurity concentration increases, resulting in transistor breakdown or internal short circuit. Transistors operating under strong RF EMFs can absorb enough energy to cause the junction temperature to exceed the allowable temperature rise and result in damage. (2) Hazards to Weapons and Equipment Modern radio transmitters and radars can generate strong electromagnetic radiation fields. This radiation field can cause installed in the weaponry system in the sensitive electronic detonation device out of control and premature start; on the guided missiles will lead to deviation from the flight trajectory and increase the distance error; on the aircraft, will cause the operating system is unstable, the heading is not allowed, the altitude of the display error, radar antenna tracking position deviation, and so on. (3) the harm of electromagnetic fields on the human body once electromagnetic radiation into the human body cells and tissues to cause biological effects, that is, the local thermal effect and non-thermal effect. Non-thermal effect mechanism is more complex, to be further explored. Thermal effect depends on the peak power of radiation, but also with the frequency. In the range of 1~3GHz, the thermal effect is the most serious, and the energy absorbed by the biological effect can reach 20%~100% of the incident energy. In other frequency ranges, the energy absorbed by the biological effect is about 40% of the incident energy. Different frequencies of electromagnetic radiation on the human body is not the same degree of harm. For radiation below 1GHz, skin tissue sensory retardation, energy permeability, easy to produce deep tissue heat and damage. For 1~3GHz radiation, the human body surface tissues and deep tissues will absorb energy, such as the eye and internal tissues are very easy to damage. The thermal effect of electromagnetic fields can make the body temperature rise, the human body over the normal body temperature, metabolism and oxygen needs quickly increase, such as temperature rise. The hazards caused by electromagnetic interference in an electromagnetic environment are varied and may range from the simplest annoying phenomena up to serious catastrophes. Two examples of the seriousness of electromagnetic interference can be illustrated by what happened in the United States. Once there was a steel mill, due to the lifting of molten molten steel ladle crane control circuit by electromagnetic interference, so that a ladle of molten steel was completely out of control dumped on the floor of the workshop, and caused casualties. In another example, a disabled person with a bioelectrically controlled prosthetic limb was driving a motorcycle under a high-voltage power line when the control circuit of the prosthetic limb was disturbed and the motorcycle went out of control, resulting in an unforeseen catastrophe. Of course, the above two examples are the more prominent ones. The following can also cite some electromagnetic interference may cause harm: a) Disturbance of television viewing, radio listening. In China, there have been due to plastic processing high-frequency thermal laminating machine interference with television viewing caused by residents and factory disputes. b) In the number of sub-systems and data transmission process data loss. c) In the equipment, sub-systems, or the destruction of the normal work of the system level. d) Medical electronic equipment (eg: medical monitoring motion, pacemaker, etc.) of the work of the malfunctioning. e) Automated microprocessor control systems (eg: automobile brake system, crash airbag protection system). f) Automated control systems (eg: automobile brake system, crash airbag protection system). (e) Automated microprocessor control systems (e.g., automobile brake systems, airbag protection systems) out of control. f) Malfunctioning of detonation devices. g) Unintentional explosions of detonation devices. h) Failure of industrial process control functions (e.g., petroleum or chemical industry). In addition to the above examples, strong electromagnetic fields can also affect living organisms, it is generally recognized that the effects can be divided into thermal and non-thermal effects. For thermal effects, with the gradual increase in RF incident power density, there can be accelerated blood flow, blood distribution less parts of the local temperature, enzyme activity, protein denaturation, heart rate changes and even thermoregulation ability to be inhibited, local tissue damage until death and so on. And for non-thermal effects. Its effects are much more extensive. These include effects on the central nervous system (e.g., metabolism of brain tissue, bioelectricity of brain tissue, etc.), on the blood and immune system, on the cardiovascular system, and on the reproductive system and embryonic development. These effects are not only at the individual and organ level, but also at the cellular level. From the above, it can be seen that the deterioration of the electromagnetic environment will lead to a variety of consequences. Developing electromagnetic compatibility research, strengthening electromagnetic compatibility management, reducing electromagnetic harassment, avoiding electromagnetic interference, is a priority.